Field of the Invention
This invention relates to cable systems used to perform different surgical procedures and, more particularly, to a system for fixing a cable in a tensioned state relative to a bone or bone fragment that is to be maintained in a desired relationship to another bone, an implant, and/or a bone fragment by the cable.
Background Art
A multitude of cable systems for surgical applications have been developed over the past several decades. The inventor herein, by himself and in conjunction with others, made a number of developments in this area over the time period between the mid-1980's and the present, many of which are the subject of U.S. patents. Among these patents are the following:
Pat. No.Issue Date7,090,675Aug. 15, 20066,730,092May 4, 20046,595,994Jul. 22, 20036,364,885Apr. 2, 20026,086,590Jul. 11, 20005,935,130Aug. 10, 19995,788,697Aug. 4, 19985,741,260Apr. 21, 19985,702,399Dec. 30, 19975,693,046Dec. 2, 19975,649,927Jul. 22, 19975,611,801Mar. 18, 19975,536,270Jul. 16, 19965,415,658May 16, 19955,116,340May 26, 19924,966,600Oct. 30, 1990The disclosure in each of these patents is incorporated by reference herein.
Cable system technology is used in performing a wide range of surgical procedures involving bone stabilization, implant stabilization, stabilization of fractured bone segments, etc.
In most of these applications, a cable length is required to be tensioned against or around components that are to be stabilized, each relative to the other, through the cable.
In the early 1980's, cable lengths were maintained in a tensioned state using basic crimp technology. That is, ends of a cable in a loop shape, extending in opposite directions, were held by a simple crimp connector that was squeezed against the surrounded cable ends.
The inventor herein developed an early system that was made from cable with a formed loop. A top hat crimp was threaded on the loose cable end after it had passed around the object, to be fixated, and through the loop. This created a lasso/noose that was tensioned, after which the top hat was crimped to maintain the cable configuration.
The next generation of cable system devised by the inventor herein, in conjunction with others, was one utilizing a crimp body at one cable end in place of the aforementioned loop that allowed the free end of the cable to be directed therethrough. The one end of the cable was swaged and threaded into a cylindrical crimp body until it locked in place. The free cable end was passed around the bone and then through the crimp body. The portion of the cable passing through the body was locked by threading a set screw into the body in a direction perpendicular to the cable length. The set screw squeezed on a crimp component on the cable to hold it in place.
The advantage of this latter system was that only a screwdriver was needed to lock the cable in place. This avoided the need for large crimpers that had to be maneuvered, generally quite awkwardly, to effect a crimp. This configuration also allowed access to difficult locations and offered a less invasive way to tension and crimp a cable.
The primary drawback with this latter system was that the set screw was oriented at 90° to the cable length. As a result, a sizable incision was required and the procedure often necessitated triangulation of a cable tensioner and a screwdriver.
The existing cable systems known to the inventor herein each has limitations that create problems or make procedures more difficult in the surgical environment. Some of these limitations are described below.
Typically, the cables will be drawn in tension using tools configured so that the tool and cable remain substantially in one plane. Crimping of the cable or fixation in any other manner is usually carried out at 90° to the plane of the cable that is normally in a loop form. This cable “locking” structure is usually reconfigured through a large, bulky, and often awkwardly operated crimper.
As described above, even with the inventor's own system, the described set screw requires the use of a screwdriver that is also operated in a direction that is generally orthogonal to the plane of the cable loop.
Another problem with early cable system tensioners is that they were often configured to pull cable from both ends. As a result, the tensioners often required a significant amount of space in which to operate.
Newer tensioning systems operate with a unidirectional capability. However, with these systems, the direction of pulling must be planned and determined ahead of time, requiring that the cable be inserted in a way that is consistent with the pulling direction. The surgeon cannot change his/her mind once the cable is passed, in which event the cable must be redirected and re-passed in the opposite direction.
A further problem with existing cable systems is that they commonly incorporate a permanently fixed component. Once a component is crimped, it cannot be released or otherwise reconfigured to allow readjustment of the cable. The only option to the surgeon is to cut the cable or components thereon to allow loosening, reapplication, or re-tensioning of the same.